The five documents listed below are incorporated herein by reference:    [1] C. Kidder and K. Chang, “Broad-Band U-Slot Patch Antenna With a Proximity-Coupled Double Π-Shaped Feed Line for Arrays,” IEEE Antennas and Wireless Propagation Letters, vol. 1, no. 1, pp. 2–4, 2002.    [2] D. H. Schaubert, “Wide-Band Phased Arrays of Vivaldi Notch Antennas,” 10th International Conference on Antennas and Propagation, no. 436, Apr. 14–17, 1997.    [3] W. R. Deal, N. Kaneda, J. Sor, Y. Qian, and T. Itoh, “A New Quasi-Yagi Antenna for Planar Active Antenna Arrays,” IEEE Trans. on Microwave Theory and Tech., vol. 48, no. 6, pp. 910–918, June 2000.    [4] M. Edimo, P. Rigoland, and C. Terret, “Wideband dual polarized aperture-coupled stacked patch antenna array operating in C-band,” Electronic Letters, vol. 30, no. 15, pp. 1196–1198, Jul. 21, 1994    [5] L. I. Parad and R. L. Moynihan, “Split-Tee Power Divider,” IEEE Trans. on Microwave Theory and Tech, vol. 13, no 1, pp. 91–95, January 1965.
Many next-generation synthetic aperture radar (SAR) imaging applications require a substantial reduction in size, weight and cost. Examples of such applications include tactical UAV-based reconnaissance and all-weather, GPS-denied precision weapon guidance. In addition to the aforementioned size, weight and cost restrictions, applications such as these also demand high performance to support extended capabilities, such as ground moving target identification (GMTI).
Conventional high resolution SARs typically employ offset-fed reflector antennas due to the wide signal bandwidth required. In such systems, the gimbal payload capacity is primarily dictated by the reflector's weight, and the radome size is largely controlled by the feed's swept path. The resulting full antenna assembly has typically been too large and heavy for next-generation applications such as those mentioned above.
Some conventional antenna construction techniques utilize photolithographic patterning and corresponding etching, which is a relatively simple and inexpensive process. Typical examples of etched antennas include Vivaldi and Yagi antennas. These antennas are constructed in three dimensions, and therefore occupy a relatively large volume.
On the other hand, patch antenna arrays are advantageously planar, which permits relatively easy fabrication of relatively small antenna arrays. Some conventional patch antenna arrays utilize U-shaped patches in conjunction with multiple proximity-coupled feeding points. Such patch antenna arrays can provide a relatively broad bandwidth capability, but do not tend to be easily reproducible.
It is desirable in view of the foregoing to provide a patch antenna array apparatus which can meet the performance requirements of next-generation applications, and which is more easily reproducible than prior art patch antenna arrays.
Exemplary embodiments of the present invention provide a patch antenna array apparatus wherein the patch antenna array and the feed network are provided together on a common substrate, thereby enhancing the reproducibility of the coupling therebetween.